Inhibitory deficits, ignoring irrelevant and attending to relevant stimuli leading to goal-directed behavior (Lavie et. al., 2004), are crucial in our understanding of information processing in PTSD and may serve as a fundamental mechanism of the disorder. If inhibitory deficits underscore the cognitive abnormalities in PTSD, then we would expect inhibition to improve with treatment, however no published studies have examined changes in inhibition. As such, the present study will examine changes in inhibition at pre- and post-treatment in individuals with chronic PTSD. Using a multi-method approach, two measures, attentional blink (Raymond, Shapiro, &Arnell, 1992), a cognitive task that examines the temporal sequence of inhibition, and pre-pulse inhibition of startle, a physiological measure that examines the strength of inhibition (Braff &Geyer, 1990), provide a more comprehensive picture of inhibitory processes. This study will compare pre and post-treatment inhibitory functioning in XX men and women with chronic PTSD who receive either 10 weeks of prolonged exposure, a cognitive behavioral therapy, or sertraline, a serotonergic medication. The goals are twofold: 1) compare changes of inhibitory functioning following a psychosocial intervention versus pharmacotherapy;and 2) compare changes in inhibitory functioning in treatment responders versus non-responders. PUBLIC HEALTH RELEVANCE: To the extent that improved inhibitory functioning is a crucial mechanism underlying PTSD recovery, inhibition should change with successful treatment.